The present invention relates to power shovels having a dipper for excavating earthen material.
There are many known earth-moving apparatuses. Typical power shovels or excavators use a bucket or dipper assembly to scoop earthen material from horizontal or vertical faces. A conventional power shovel has a boom, and the dipper is mounted on the boom via a crowd mechanism. The crowd mechanism includes a crowd pinion on the boom, and crowd rack as part of the dipper handle which pivots about the pinion and which moves translationally along the pinion. The dipper is mounted on the end of the handle. The bucket or dipper is normally provided with sharp teeth to provide a digging action against the surface being worked and further includes a cavity for collecting the material so removed. Once the earthen material is received within the dipper, the dipper is typically moved to another location for transfer of the material. The material is usually discharged into a dump truck, onto a conveyor, or merely onto a pile.
Each of the dippers in these power shovels typically has orthogonal sides and a heel band that is mounted on a lower end of the dipper. The heel band is essentially a wear bar attached to the lower end of the front wall of the dipper to prevent excess wear on the dipper walls by contact with earthen material during excavation. Each dipper typically has a lip at the top of the front wall to accommodate attachment of teeth to the dipper.
A lip angle is defined as the angle between the front wall of the dipper and the lip and is typically between ten and eighteen degrees. The plane of the teeth usually coincides with the lip and forms a tooth angle with an imaginary line drawn tangent to the pitch line of the crowd pinion and intersecting the upper surface of the lip, the tooth angle being between 46 and 50 degrees when crowd rack is fully extended. One known power shovel construction has a lip angle of three to five degrees but a tooth angle of greater than 50 degrees. In some prior art dippers with a zero to five degree lip angle, the front and rear dipper walls are not parallel, creating a sort of funnel in the dipper because the area of the top opening of the dipper becomes larger than the area of the bottom opening of the dipper.
One problem with conventional dippers is the inordinate wear on the heel band at the lower end of the dipper as the dipper is repeatedly drawn through earthen material. Another problem with conventional dippers is the incomplete filling of the dipper on each pass, resulting in an inefficient use of the power shovel. Previous attempts at altering the shape of a dipper have resulted in material clogging due to the creation of a funnel-like dipper where the top opening is larger than the bottom opening or resulting in a tooth angle outside the recommended limits for desirable angle of attack relative to earthen bank.
The invention provides a skewed dipper shape to protect the heel band from wear, thus reducing the required replacement frequency of the heel band. The invention also provides a skewed dipper that is capable of being substantially completely filled in every pass so that a minimum number of dipper passes are needed to move a given amount of earth. At the same time, the area of the material receiving opening at the top of the dipper is substantially identical to the area of the material discharging opening at the bottom of the dipper, allowing material to pass through the dipper unimpeded.
In particular, the invention provides a power shovel including a frame, a boom mounted on the frame, and a crowd drive, mechanism mounted on the boom, the mechanism including a crowd pinion having a pitch diameter. The power shovel also includes a dipper handle supported by the crowd mechanism for translational movement relative to the boom and for pivotable movement relative to the boom. A dipper is connected to the handle for movement therewith, the dipper including a generally planar front wall defining a plane and having an upper edge, and a generally planar lip defining a plane and arranged along the upper edge of the front wall, the lip having an upper surface. The plane of the lip forms a lip angle with the plane of the front wall, the lip angle being between three and five degrees. The plane of the teeth is usually in line with the plane of the lip forms a tooth angle with an imaginary line drawn tangent to the pitch diameter of the crowd pinion and intersecting the upper surface of the lip where the tooth is attached, the tooth angle being between 46 and 50 degrees.
In addition, the invention provides a power shovel including a frame, a boom mounted on the frame, and a crowd drive mechanism mounted,on the boom, the mechanism including a crowd pinion having a pitch diameter. The power shovel also includes a dipper handle supported by the crowd mechanism for translational movement relative to the boom and for pivotable movement relative to the boom. A dipper is connected to the handle for movement therewith, the dipper defining a material receiving opening and a material discharging opening, each opening being generally rectangular and having an area, the areas of the receiving and discharging openings being substantially identical. The dipper includes a generally planar back wall defining a plane and including a lower end, a generally planar front wall defining a plane, the front wall being opposite to the back wall and substantially parallel to the back wall, the front wall having an upper edge, and generally trapezoidal and substantially parallel side walls connecting the back wall and the front wall. The dipper also includes a dipper door that defines a plane and that is mounted on the lower end of the back wall for pivotable movement relative thereto for opening and closing the discharging opening. The plane of the door and the plane of the back wall form a right angle when the door is closed, and the plane of the door and the plane of the front wall form a right angle when the door is closed.
Because the dipper is skewed, the heel band is approximately twelve inches behind where it would be in an orthogonal prior art dipper. As a result, the heel band experiences less wear because it is at least partially elevated away from the digging path followed by the dipper especially during initial crowd thrust into the bank.
Additionally, the skewed shape of the dipper allow for greater penetration of the dipper lower into an earthen bank because heel band interference with the earthen bank is dramatically curtailed. This is especially advantageous in shallow bank applications where good dipper fill factors are difficult to achieve.
Further, the skewed shape of the dipper allows the power shovel to extend the reach of the dipper teeth along the floor directly in front of the power shovel, extending the flat floor reach (limits) on which the power shovel can move. There is less of a need for bulldozers to clean up the floor in front of the power shovel. As a result, the power shovel may also be maneuvered closer to the bank.
Further, the skewed shape of the dipper allows more space for the dipper to be moved down and back toward the power shovel because the heel band has more clearance from the front of the power shovel track.
Further, the skewed shape of the dipper allows users to investigate the advantages of decreasing the tooth angle below 46 degrees in certain types of sticky material. Without the skew this cannot be done without drastically aggravating heel band interference with the bank.
Finally, the skewed shape of the dipper allows the earth it has dug up to more completely fill the dipper and the power shovel to more efficiently move earth due to fewer necessary digging cycles.
Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims, and drawings.